On the verge of firing by a president who has said she isn’t a strong enough defender of the U.S.-Mexico border, Nielsen has adopted — and made sure to publicize — a tough stance in response to the caravan of Central American migrants headed toward the U.S. that Trump turned into a major midterm campaign issue. She has visited the southern border three times since October, and recently hailed Trump as a forceful “leader.”

The firm posture seems to have impressed her most important audience: the president.

Five sources inside and close to the administration describe a clear shift in the president’s feelings toward his DHS chief, about whom he has repeatedly complained over the past year. Her fate is of particular interest because, administration officials say, White House chief of staff John Kelly, a longtime Nielsen mentor and defender, could quickly follow her out the door in frustration.